In a previous project, the investigators included 40 patients with single domain amnestic MCI (Mild Cognitive Impairment), known to be at high risk for AD and demonstrated that aMCI patients with a profile of subhippocampal dysfunction (impaired performance on a visual recognition memory task) display other clinical as well as imaging profiles of patients with early AD using MRI and SPECT. Longitudinal follow-up data in these patients is currently under way. Preliminary data indicates that evaluating the subhippocampal region using visual recognition tasks is highly predictive of AD over 6 years.